Title: Evaluation of insecticides for control of fall armyworms on sweet corn.
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 Material Information
Title: Evaluation of insecticides for control of fall armyworms on sweet corn.
Series Title: Evaluation of insecticides for control of fall armyworms on sweet corn.
Physical Description: Serial
Language: English
Creator: Foster, R. E.
Publisher: Everglades Research and Education Center.
Place of Publication: Belle Glade, Fla.
Publication Date: 1984
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Bibliographic ID: UF00076913
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 166141203

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EV1985-4 March 1985


Evaluation of Insecticides for Control
of Fall Armyworms on Sweet Corn Fall, 1984


R.E. Foster
Everglades Research and Education Center


Materials and Methods

The sweet corn variety Florida Staysweet was planted on October 12,

in a muck field at the EREC. The row width was 36 inches with approxi-

mately 8 inches between plants within the row. The plots were 4 rows

wide and 25 feet long. The experimental design was a randomized com-

plete block with 4 replications. The treatment sj 1$ te1

Lannate was applied to treatments 11, 12, and 3 begin at tassel

emergence on November 28. Liquid treatments re applied with a tract r-

mounted boom sprayer at 60 psi in 33.1 gallon QF A. te

in the season with a backpack sprayer at 35 psi at the same gallonage.

Granular treatments were applied manually over the row. The initial

treatments were made on October 24. Fifteen treatments were made to all

plots except treatment 8 (PP321 at 0.030 lb ai for residue analysis)

which received 21 treatments. The treatment schedule is given in Table

2.

Seven days after the initial treatment, 10 plants were removed from

each plot. Each plot was given a visual damage rating as follows:

1 = No Damage

2 = Slight Damage

3 = Moderate Damage

4 = Severe Danage

5 = Very Severe Damage

;:lach ;.laht then as' carefully dissected and the number of live larvae

cou:ited. Larvae less than 3/1 inch long were considered smrcall larvae

and larvae greaterr than 3/?J inch loan vere considered large larvae.






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On riecccTrIr 19, 10 pTlants front each. nlot T.ere rated for cdanace u ,in, the

1--5 scale. On January 1*,, 1:, 25 cars ".ere rc' .oved from each lot,.

":ar.ia::e .a. clanisfied ns ti-.a-..l .t~. if it warn co- fi) c. to the tCr'in&.l 1

incl. of tLe ar. ::vy cav7ir.a;. rather th:an i nc'. fror tei ti' rcsultrez

ii the ear rci; clanrfic. ac, a- u..aret, lc ear. Thi infestation

consisted ri.';arily of fall arnyvorn-., w7it'l.h oie vy.cllo,-ctrinedC. anrr--

T7orp.:"

'.aOlec ilt

iT-e cto,.;. r' 31 evaluatiovr of the initial spray recult1e i. no

si:iificant _i.ffronc(! e ih. thCe n.i.uers of Call larv'. .hre ere,

io--'ver, i:' :ificat differe--:ccsi iTn t'he a ruyer of lare larvae an-.. total

larvae ('.able ). T.. rz..ults of tie larval co!unto are rnt!:.nr (iffi-

cult to i.ter.reft., -iukce .i-vaer rather of a at: culvr'tici

sor:'2ti!ii. .' less co,'.trol tT.:P't a lo'Cor ri.tc. T"'A.le co:.fusionv, ir pro-

bably uue to un-0 v'nfC-e of 't larval infctio.. The recults ro. hae

Ja-.:ar. rat:inc' arae :ro: a'-1. ;'.ore ,ar-i;::l, aiLt'.ouI.?. c:ae of the _i.n-

cr- ?c.:ci. ; still r-:ani ('ablc 4). e da.e ..- ration. are a. c a.ccourate

reflectic..: of t-.i visual a caraicc of thk-.' lot. L:. u i:.tr ,td .lots

-ere. :evernel: ... n:..- t':. LtanLate -lotc loo:' ':e on.e t:..ar. tie other

trcatr,..tf2. t ~t oc of t'_c da:-aIe to thei...-. 2tt-- e atreat".'e.'t, Ie: .roLa'1ly

occurred. :rior to tT e l::t atilcatio-..

The .'ecer:-.'r I." ,a .-;a-in rLit-i s :ave an ave:n .,ett'-c evaluation of

t.e de,2rze of control caford-er t various t V resat.nts y thc tiIn,

11 rplicacion. : en i.ae (1 for 'rca: :. t ... ) four ..... e t

rates of Th3:1, Larvi:!... a-.. .rvi.-/y.:"-: forv'.W t. to.. rou..

The check :., t La_,.' tro.t:.eT.?t a- the 1 .' ratc. of ct .O,-i V:'

forn.;el tl" ott-o:: -.:ou-,. tl. ro-...:.i-:'.r o' t : tr .-t.: '-:;.t. "-re i:ter--

, mediate. .i:. ur 1 .o" t o .i of .:.i:. r i:"- of tC...e

ra of .... or "o tf c' r I r. -^" *;-"c *n. *.0 :: n 'i io-'.o






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relationship, probably because of damage that occurred prior to the

application of the insecticides. However, by December 19 there was a

very strong relationship between the rate and the damage rating, as evi-

denced by the correlation coefficient of 0.88.

The harvest evaluations are probably not as meaningful as the

December 19 damage ratings. However, they do show that PP321 at 0.015

lb ai/A or above and both formulations of Larvin provided excellent ear

protection. All treatments that relied on Lannate for ear protection

suffered more ear damage than those protected by PP321 or Larvin. Had

it been possible to measure the yields, the differences would have been

more striking, probably similar to the December 19 damage ratings.

Future evaluations of this type will include yields.

Discussion

The experimental compound PP321 appears to be a very promising

material for fall armyworm control. The 0.010 lb ai/A rate may be too

low to provide the level of control necessary for fresh market sweet

corn. The higher rates all gave excellent control. Lannate 1.8L, a

standard sweet corn insecticide, gave mediocre control, although sig-

nificantly better than the check. Both rates of Lannate suffered a

significant amount of damage, but the 1 pint rate gave inadequate ear

protection. The use of Methomyl 5G prior to tassel emergence gave

better protection of the plant than Lannate 1.8L, but not as good as

some of the other compounds. The 20 lb/A rate gave control comparable

to Larvin 3.2 E.C.

Both formulations of Larvin gave excellent control of armyworms,

although it appears that the 80 DF formulation may be slightly superior

to the 3.2 EC formulation. Switching from Larvin 3.2 EC to Lannate at

tassel emergence resulted in poorer control than using Larvin throughout

the season with the spray schedule used.





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In conclusion, despite the severe potential for fall armyworm

damage, sweet corn can be grown in the Everglades area if repeated in-

secticides applications are made. Five of the treatments in this trial

produced 100% clean ears and several other treatments had only low

levels of damage. This would indicate that it may be possible to get by

with fewer than the 15 applications used in this study. Future studies

will look at the possibilities for fewer insecticide applications as

well as evaluating the efficacy of available insecticides.







Table 2. Treatment Schedule Corn Trial: Fall, 1984.


Oct.
Oct.
Oct.
Nov.
Nov.
Nov.
Nov.
Nov.
Nov.
Nov.
Nov.
Nov.
Dec.
Dec.
Dec.
Dec..
Dec.
Dec.
Dec.,
Dec.
Dec.
Dec,,
Dec.
Jan.
Jan.
Jan.


Corn planted
All plots
Larval counts, damage ratings
All plots
All plots
Residue only
All plots
Residue only
All plots
Residue only
First tassels emerging
All plots
All plots
Residue only
Residue only
All plots
All plots
All plots
All plots
Damage ratings
All plots
All plots
All plots
All plots
Residue only
Harvest







Table 3. Number of
10 plants
secticide


large larvae (>3/8 inches) and total larvae per
on October 31, seven days after initial in-
application.


Mean No.
Large Larvael


Mean No.
Total Larvael


PP321
PP321
Lannate
PP321
PP321
Larvin 80DF
Methomyl 5G
Lannate
Methomyl 5G
Larvin 3.2
PP321
Larvin 3.2
Check


0.015 lb ai
0.020 lb ai
1 pint
0.030 lb ai
0.010 lb ai
0.75 lb ai
20 lbs
2 pints
10 lbs
0.75 lb ai
0.025 lb ai
0.75 lb ai


1Means followed by the same letter
at the 0.05 level.


are not significantly different


Treatment


Rate/A


2.75
3.00
3.50
3.75
4.25
4.25
5.25
6.25
6.50
6.75
7.50
9.50
16.25


5.00
5.18
6.25
5.88
6.63
6.75
7.73
9.38
9.13
9.40
9.98
12.08
21.00








Table 4. Damage ratings (1-
trial, October 31.


5 scale) for sweet corn insecticide


Compound


Rate/A


PP321
PP321
PP321
PP321
PP321
Methomyl 5G
Larvin 80DF
Larvin 3.2
Methomyl 5G
Larvin 3.2
Lannate
Lannate
Check


0.030 lb
0.020 lb
0.015 lb
0.010 lb
0.025 lb
20 Ibs
0.75 lb
0.75 lb
10 lbs
0.75 lb
1 pint
2 pints


Damage Ratingi


2.125
2.175
2.250
2.375
2.475
2.475
2.500
2.575
2.625
2.650
2.750
3.125
4.850


a
a
a
a
a
a
ab
ab
ab
ab
ab
b
c


1Means followed by the
at the 0.05 level.


same letter are not significantly different







Table 5. Damage ratings (1-5 scale) for sweet
trial, December 19.


corn insecticide


Damage Ratingi


PP321
PP321
PP321
Larvin 80DF
PP321
Larvin/Lannate
PP321
Methomyl 5G/Lannate
Larvin 3.2
Methomyl 5G/Lannate
Lannate
Lannate
Check


0.030 lb ai
0.020 lb ai
0.025 lb ai
0.75 lb ai
0.015 lb ai
0.75 lb/2 pints
0.010 lb ai
20 lbs/2 pints
0.75 lb ai
10 lbs/2 pints
2 pints
1 pint


Rate/A


1.125
1.175
1.300
1.375
1.425
1.450
1.575
1.650
1.675
2.150
2.175
2.250
3.800


1Means followed by the same letter are not significantly dif-
ferent at the 0.05 level.







Table 6. Harvest evaluation of Spodoptera spp. damage to sweet
corn ears.


% Totally % Market-
Compound Rate/A Clean Ears able Ears1,2


8. PP321 0.030 lb ai 100 a 100 a
9. Larvin 80DF 0.75 lb ai 100 a 100 a
6. PP321 0.020 lb ai 100 a 100 a
7. PP321 0.025 lb ai 100 a 100 a
5. PP321 0.015 lb ai 100 a 100 a
10. Larvin 3.2 0.75 lb ai 99 a 99 a
4. PP321 0.010 lb-ai 97 a 98 ab
3. Lannate 2 pints 96 ab 98 ab
13. Methomyl 5G/Lannate 10 lbs/2 pints 96 ab 100 a
12. Methomyl 5G/Lannate 20 lbs/2 pints 95 ab 96 ab
11. Larvin/Lannate 0.75 lb ai/2 pints 94 ab 97 ab
2. Lannate 1 pint 90 b 93 b
1. Check 43 c 55 c


leans followed by the same
the 0.05 level.


letter are not significantly different at


2Ears were considered marketable if they were totally clean or if the
damage was confined to the terminal 1 inch of the ear.




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